8.2

 Chemical reactions are continually occurring in our bodies to keep us alive.  These chemical reactions must occur at low temperatures so that cells in our body are not damaged.  Catalysts – are chemicals that increase the rate of reactions without increasing the temperature or changing the substance being made  Proteins in our bodies that act as catalysts are called enzymes.

 Enzymes also help reactions occur at a lower energy level.  Enzymes are not changed during a reaction.  Enzymes can be identified by an “ase” ending i.e protease, lipase

 The structure the enzyme binds to is called the substrate.  The area on the enzyme where the substrate binds is called the active site.  There is a different active site for every enzyme – substrate combination  Once the substrate is bound the enzyme then helps to change the substrate into the product.

 Cofactors and coenzymes are enzyme helpers.  They help the enzyme bind to the substrate  Cofactors are inorganic – iron, zinc, potassium  Coenzymes are organic – made from vitamins

pH  different enzymes function the best at different pH levels, there is a range for each enzyme  if the solution is too acidic (high H+ levels), or too basic (high OH - ) the hydrogen bonds that determine the enzymes structure will change.  a change in enzyme structure will affect its function

Substrate Molecule Concentration  The greater the number of substrates the greater the number of interactions (more substrates will bind with enzymes)  This increase will plateau when all of the enzymes are bound to a substrate

Temperature  As the temperature increases the number of substrate – enzyme interactions increase and more products are made  In humans the temperature cannot exceed 37 ◦ - why do you think this is the case?  too much heat will cause denaturation of the enzyme

Competitive Inhibitors  Competitive inhibitors resemble the substrate  The inhibitor binds to the enzyme, preventing the enzyme from binding to the substrate

 The production of chemicals in our bodies (e.g. hormones) follows a metabolic pathway with enzymes helping along the way  The production of chemicals in our body is regulated by our bodies need for that chemical A) Feedback Inhibition – the inhibition (stopping) of an enzyme in a metabolic pathway by the final product of the pathway.

 The final product binds to the regulatory site of the enzyme preventing it from binding to any more substrates

B) Precursor activity – the activation of the last enzyme in a metabolic pathway by the initial substrate  This occurs to help speed up the reaction when there is a build up of the initial substrate  The binding of the initial substrate to the enzyme improves the enzyme-substrate fit Note: both feedback inhibition and precursor activity involve molecules binding to the regulatory sight of the enzyme

 Both feedback inhibition and precursor activity are called allosteric activities  Allosteric activity is a change in an enzyme caused by the binding of a molecule

 questions 1-3 and 5  page 258